Sequential unique marking

ABSTRACT

The present invention comprises a method of sequential unique marking comprising providing a multi-die handling device with a plurality of semiconductor devices therein, reading an ID code on the multi-die handling device, retrieving a tray map file corresponding to the ID code, determining a tray matrix of the multi-die handling device, retrieving data from the tray map file, the data comprising unique characters correlating to each semiconductor device of the plurality of semiconductor devices, and marking each semiconductor device with the data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/916,679,filed Aug. 11, 2004, now U.S. Pat. No. 6,996,484, issued Feb. 7 2006,which is a continuation of application Ser. No. 09/928,032, filed Aug.10, 2001, now U.S. Pat. No. 6,792,365, issued Sep. 14, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The current invention relates generally to marking semiconductor dicehaving integrated circuits (ICs) and, more specifically, to a system foruniquely marking exterior surfaces of semiconductor dice in lots.

2. State of the Art

In conventional semiconductor device fabrication processes, a number ofdistinct semiconductor devices, such as memory chips or microprocessors,are fabricated on a semiconductor substrate, such as a silicon wafer.Each semiconductor wafer has a plurality of integrated circuitsemiconductor dice (IC) arranged in rows and columns with the peripheryof each IC being substantially rectangular or square. After the desiredstructures, circuitry, and other features of each of the semiconductordevices have been fabricated upon the semiconductor substrate, thesubstrate is typically singulated to separate the individualsemiconductor devices from one another.

While semiconductor dice may carry information on the active surfacethereof regarding the manufacturer, specifications, etc., suchinformation cannot be easily read without the use of optical devices.Therefore, subsequent to the wafer dicing process, individualsemiconductor dice are commonly subjected to a marking process whereinvarious easily read information is placed on the backside or inactiveside of the semiconductor die for purposes of corporate identity,product differentiation and counterfeit protection.

Currently, the preferred method of marking packaged semiconductor diceis using a laser beam. Lasers are used to mark semiconductor dice with amanufacturer's logo, as well as alphanumeric marks and bar codesspecifying the company's name, a part or serial number, or otherinformation such as lot or die location. In particular, lasers havebecome especially useful in marking high volume production items such asbare or packaged semiconductor dice. The high speed and precision oflaser marking makes their use highly desirable for high throughputautomated processes. Unlike the previously utilized technique of inkstamping, laser marking is very fast, requires no curing time, producesa consistently high quality mark, and can take place at any point in themanufacturing process.

Traditionally, semiconductor devices are marked as a group of 25 to asmany as 50 devices having similar parameters. Singulated semiconductordevices are characterized for compliance with certain criteria in orderto determine their suitability, or lack thereof, for different potentialuses. For example, devices may be separated based on operating speedwherein devices performing above a particular speed are placed in onegroup while devices functioning at a slower speed are placed into adifferent group. Carriers such as tubular magazines or bins 200 can beused to physically separate groups of devices 250 (FIG. 3). However,these carriers are unsuitable for recently developed semiconductorpackages that are much-reduced in size, thickness and dimensions ofindividual features, such as leads for external connection tohigher-level packaging.

One example of such state-of-the-art semiconductor device packages is athin plastic package configuration identified as a Thin Small OutlinePackage, or TSOP. Another example is a Thin Quad Flat Pack, or TQFP. Byway of comparison, such packages are dimensioned with a total packagethickness, excluding lead fingers, of less than about one-half thethickness of a conventional plastic Small Outline J-lead package, orSOJ. These newer semiconductor device packages, with their smallerdimensions and more fragile components, are much more susceptible toinadvertent damage in handling than prior package designs and, at best,are only marginally robust enough for handling in tubular magazines. Asa result, the industry has gravitated to processing such relativelydelicate semiconductor packages in batches carried in recesses ofrectangular trays, one example of which are so-called JEDEC trays 100(FIG. 1). Other, even smaller semiconductor packages under currentdevelopment and most recently introduced to the market include so-called“chip scale” semiconductor packages. These packages, having dimensionsapproximating those of a bare semiconductor die itself and employingextremely minute external connection elements, also are desirablyhandled in trays.

As stated, groups or lots of semiconductor devices or bare semiconductordice consist of a particular device type and are selected to meetcustomer or industry standard specification. After sorting,semiconductor dice are typically marked as a group such that allsemiconductor dice receive the same mark. Semiconductor dice generallyundergo an array of testing during the manufacturing process and groupsof semiconductor dice can be tracked through the fabrication, probe,assembly and test steps. However, this so-called lot-based manufacturinghas several limitations including that it is inefficient, expensive,unreliable and impossible to achieve truly unique marking ofsemiconductor devices.

As a lot of semiconductor dice bearing the same identification numberpasses through manufacturing, data associated with the lot is generatedand stored in association with the lot number. It is critical to trackall semiconductor dice individually in a particular order so that testresults can be correlated with the proper die. However, manufacturersmust balance the benefit of identifying problems within individualsemiconductor dice with the fact that maximum efficiency is achievedwhen a large number of semiconductor dice are tested in succession andproblems are addressed only after the testing is complete. Accordingly,semiconductor dice are tested and results are recorded sequentially. Tomaintain accurate results, semiconductor dice must be placed and storedin carrier tubes in the identical order. The potential for error inlot-based manufacturing is very high as one misplaced semiconductor dieor carrier results in inaccurate data association.

U.S. Pat. No. 5,856,923 to Jones et al. discloses a method of continuousnonlot-based integrated circuit manufacturing. In this process, eachdevice from a mixed lot is provided either a substantially unique fuseID code or marked on the lead frame with a substantially unique ID code(U.S. Pat. No. 6,049,624 to Wilson et al.). The devices are processedand process-related data is generated for each individual device. Datarelating to the particular device, rather than the entire lot, is storedin association with the substantially unique ID code.

U.S. Pat. No. 6,049,624 to Wilson et al. further discloses markingcarrier trays or storage shelves with an ID code and storing the carriertray ID code in association with the ID code for semiconductor dice.Semiconductor dice can be retrieved by lot number from the shelves orcarrier trays.

It would be an improvement in the art to develop a technique of in-traymapping and sequential unique marking of packaged semiconductor devicesor bare semiconductor dice that eliminates the need for them to bepre-sorted.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present invention includes a method of sequentialunique marking comprising providing a multi-die handling device with aplurality of packaged semiconductor devices or bare semiconductor dicetherein, reading an ID code on the multi-die handling device, retrievinga tray map file corresponding to the ID code, determining a tray matrixof the multi-die handling device, retrieving data from the tray mapfile, the data comprising unique characters correlating to eachsemiconductor device or semiconductor die of the plurality ofsemiconductor devices or semiconductor dice and marking eachsemiconductor device or semiconductor die with the data.

Another embodiment of the present invention includes a method of cullingsemiconductor devices or bare semiconductor dice from a reject bin. Themethod includes retrieving a plurality of semiconductor devices or baresemiconductor dice from a reject bin, providing a plurality of multi-diehandling devices having a plurality of pocket locations and assigningeach multi-die handling device an ID code. Each semiconductor device orbare semiconductor die is placed in a pocket location of the pluralityof pocket locations. The semiconductor devices or bare semiconductordice are tested and a tray map file comprising test data is generated.The tray map file is stored in association with the ID code of themulti-die handling device. The method further includes reading the IDcode on a multi-die handling device, retrieving the tray map filecorresponding to the ID code, determining a tray matrix of the multi-diehandling device, retrieving unique test data from the tray map file andmarking each semiconductor device or bare semiconductor die of saidplurality of semiconductor devices or bare semiconductor dice with thecorresponding test data.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a common JEDEC tray for carrying multiple devices;

FIG. 2 is a flow chart of sequential unique marking of the presentinvention; and

FIG. 3 illustrates a perspective view of a tray shuttle including amagazine carrier.

DETAILED DESCRIPTION OF THE INVENTION

Tray mapping is the logical assignment of pocket locations within theboundaries of a multi-die handling device, such as a JEDEC tray 100shown in drawing FIG. 1. The purpose of tray mapping is to establish acorrelation between the location of devices in a tray and the trayitself. This positional relationship of devices in a tray is importantas it directly relates to test result data created by in-tray testequipment.

As shown in drawing FIG. 1, a JEDEC tray 100 consists of pocketlocations 110 in rows and columns (X- and Y-axis coordinates). Eachpocket location 110 is assigned a unique coordinate number based on itsX- and Y-axis coordinates. In the example shown, pocket locations 110receive a unique whole number (i.e., 1.0, 2.0, 3.0) corresponding to itslocation along the X-axis and a unique fractional number (i.e., 0.1,0.2, 0.3) corresponding to its location along the Y-axis. While thecurrent invention is described using a JEDEC tray 100, it will beunderstood by those of skill in the art that the invention is applicableto any multi-die handling device including multi-die handling deviceshaving vertical carrier capabilities (e.g., a multi-die handling devicethat can store dice along X-, Y- and Z-coordinates). Further, as usedherein, the terms “tray,” “carrier” and “multi-die handling device” areused interchangeably.

It will be further understood by those having skill in the field of thisinvention that the present invention is applicable to any IC device,including Dynamic Random Access Memory (DRAM) ICs, Static Random AccessMemory (SRAM) ICs, Synchronous DRAM (SDRAM) ICs, processor ICs, SingleIn-Line Memory Modules (SIMMs), Dual In-Line Memory Modules (DIMMs), andother Multi-Chip Modules (MCMs).

The presently claimed invention includes a method of quickly placingunique characters, as well as non-unique characters, on everysemiconductor device in a tray matrix. Preferably, semiconductor devicesare marked by a laser having a six-inch mark field which allows astandard JEDEC tray 100 to be marked in half the amount of time.Examples of unique characters include, but are not limited to, test dataextracted from a tray map file, for example, four characters [2 bytes inHex (FAFA)] may represent test data unique to each semiconductor devicein the tray.

Examples of non-unique characters include, but are not limited to,semiconductor device data (dynamic objects) and graphics (staticobjects) common to all the semiconductor devices in the tray. Furtherexamples of non-unique characters include, but are not limited to, datecode, semiconductor device type, country code, and company logo.

A tray map file, according to the present invention, may include a fileincluding test data collected during in-tray testing of semiconductordice. By way of example, semiconductor devices that do not meet specificcriteria during initial processing are often discarded into reject binsand certain manufacturers are increasingly relying upon salvagingsemiconductor devices from reject bins. All of the previously rejectedsemiconductor devices must be tested to characterize the devices anddetermine their suitability for use. Preferably, these semiconductordevices, from mixed lots and with unknown parameters, are placed in amulti-die handling device and tested “in-tray.” Test results arepreferably stored as data in a tray map file wherein the data is storedin association with a particular pocket location. Each carrier ormulti-die handling device is assigned an optically readable ID code andthe tray map file is stored in association with the ID code.

Illustrated in drawing FIG. 2 is a flow-chart of sequential uniquemarking of the current invention. The process of sequential uniquemarking can take place either before or after packaging of semiconductordice. In step 10, the optically readable ID code, or barcode, on themulti-die handling device or tray is read and the corresponding tray mapfile is retrieved. The tray matrix and the number of cells, or pocketlocations, are determined in step 20. For example, in the JEDEC tray 100shown in drawing FIG. 1, the matrix includes rows and columns as shownby the X-axis and Y-axis. The number of cells is equal to the number ofrows times the number of columns. Those skilled in the art willappreciate that the step of determining the tray matrix may include athird Z-axis.

Data from the tray map file is retrieved in step 30. As stated above,the tray map file preferably includes the results, or device parameters,of in-tray testing. The device in the current cell is marked with thetray map data in step 40. Various laser marking methods are known in theart. The methods of efficiently laser marking singulated semiconductordevices as described in U.S. Pat. Nos. 5,986,235 and 5,937,270, andassigned to the assignee of the presently claimed invention, areincorporated herein by this reference. Further, U.S. Pat. No. 6,417,484,assigned to the assignee of the present invention and herebyincorporated herein by this reference, discloses a laser marking systemfor dice carried in trays and method of operation.

After the semiconductor device is marked, it is determined whether thecurrent cell is the last cell on the tray in step 50. If there isanother cell on the tray, the process moves to the next cell on the trayin step 60 and steps 30 through 50 are repeated. When the last cell onthe tray is reached, it is determined whether any other trays exist instep 70. If additional trays are present, steps 10 through 50 arerepeated. When the last tray is reached, sequential unique marking iscomplete 90.

At the end of the process described, all of the semiconductor devices ina multi-die handling device receive sequential unique markings using onemark command. One advantage of the present invention is the eliminationof the need to pre-sort devices before marking. By marking devices withtest data, preferably related to device parameters, truly unique markingis achieved. Further, the presently claimed invention creates a “virtualbinning” of devices, wherein the parameters of each semiconductor deviceare known and associated with a specific location within a multi-diehandling device.

Although the foregoing description contains many specifics, these shouldnot be construed as limiting the scope of the present invention butmerely as providing illustrations of some of the presently preferredembodiments. Similarly, other embodiments of the invention may bedevised which do not depart from the spirit or scope of the presentinvention. Features from different embodiments may be employed incombination. The scope of the invention is, therefore, indicated andlimited only by the appended claims and their legal equivalents, ratherthan by the foregoing description. All additions, deletions andmodifications to the invention as disclosed herein which fall within themeaning and scope of the claims are to be embraced thereby.

1. A method of culling semiconductor devices, comprising: retrieving aplurality of semiconductor devices from at least one reject bin;providing at least one carrier having a plurality of pocket locations;assigning an ID code to the at least one carrier; placing eachsemiconductor device of the plurality of semiconductor devices in apocket location of the plurality of pocket locations; testing eachsemiconductor device of the plurality of semiconductor devices todevelop corresponding test data; generating a tray map comprising the IDcode and the corresponding test data of each semiconductor device of theplurality of semiconductor devices; and marking each semiconductordevice of the plurality of semiconductor devices with a unique markingrepresenting the corresponding test data.
 2. The method of claim 1,further comprising: storing the tray map as a tray map file; reading theID code on the at least one carrier; retrieving the tray map filecorresponding to the ID code; and retrieving the corresponding test datafrom the tray map file for at least one semiconductor device of theplurality of semiconductor devices.
 3. The method of claim 1, whereinmarking further comprises marking each semiconductor device of theplurality of semiconductor devices with a non-unique marking, thenon-unique marking including one or more items selected from the groupconsisting of semiconductor device data, date code, country code, andcompany logo.
 4. The method of claim 1, wherein the corresponding testdata comprises characterization data indicating at least one deviceparameter for at least one semiconductor device of the plurality ofsemiconductor devices.
 5. The method of claim 1, wherein eachsemiconductor device of the plurality of semiconductor devices comprisesa semiconductor device selected from the group consisting of DynamicRandom Access Memory (DRAM) semiconductor devices, Static Random AccessMemory (SRAM) semiconductor devices, Synchronous DRAM (SDRAM)semiconductor devices, processor semiconductor devices, Single In-LineMemory Modules (SIMMs), and Dual In-Line Memory Modules (DIMMs).
 6. Themethod of claim 1, wherein marking occurs before packaging eachsemiconductor device.
 7. The method of claim 1, wherein marking occursafter packaging each semiconductor device.
 8. A method of cullingsemiconductor devices, comprising: retrieving a plurality ofsemiconductor devices from at least one reject bin; providing aplurality of carriers, each carrier of the plurality having a pluralityof pocket locations configured in a tray matrix; assigning an ID code toat least one carrier of the plurality of carriers; placing eachsemiconductor device of the plurality of semiconductor devices in apocket location of the plurality of pocket locations; testing eachsemiconductor device of the plurality of semiconductor devices todevelop corresponding test data; generating a tray map for each carrierof the plurality of carriers, the tray map comprising the ID code andthe corresponding test data of each semiconductor device of theplurality of semiconductor devices; and marking each semiconductordevice of the plurality of semiconductor devices with a unique markingrepresenting the corresponding test data.
 9. The method of claim 8,further comprising storing the tray map as a tray map file.
 10. Themethod of claim 8, wherein marking further comprises marking eachsemiconductor device of the plurality of semiconductor devices with anon-unique marking, the non-unique marking including one or more itemsselected from the group consisting of semiconductor device data, datecode, country code, and company logo.
 11. The method of claim 8, whereinthe corresponding test data comprises characterization data indicatingat least one device parameter for at least one semiconductor device ofthe plurality of semiconductor devices.
 12. The method of claim 8,wherein each semiconductor device of the plurality of semiconductordevices comprises a semiconductor device selected from the groupconsisting of Dynamic Random Access Memory (DRAM) semiconductor devices,Static Random Access Memory (SRAM) semiconductor devices, SynchronousDRAM (SDRAM) semiconductor devices, processor semiconductor devices,Single In-Line Memory Modules (SIMMs), and Dual In-Line Memory Modules(DIMMs).
 13. The method of claim 8, wherein marking occurs beforepackaging each semiconductor device.
 14. The method of claim 8, whereinmarking occurs after packaging each semiconductor device.